JP2009194173A - Microwave plasma processor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To make appropriate a shape of a surface on the processing body side of a dielectric plate in response to a gas type. <P>SOLUTION: A microwave plasma processor 100 includes a plurality of dielectric plates 31 on the ceiling face. On a lower face of the dielectric plates 31, seven recessed parts are formed. A state of a standing wave inside the dielectric plates indicates a distribution of an electric field energy inside the dielectric, and changes in response to a reflected wave rp from a plasma. The reflected wave rp from the plasma changes in response to the gas type, and is represented by a permittivity ε<SB>r</SB>and dielectric dissipation factor T<SB>δ</SB>of the plasma. Thus, the standing wave inside each dielectric plate changes according to the gas type, and its state is inferred from the permittivity ε<SB>r</SB>and dielectric dissipation factor T<SB>δ</SB>of the plasma. Based on a result inferred in this manner, projected parts between recessed parts on the lower face of the dielectric plates 31 are flattened so that an energy conducts from a strong region of the electric field energy to a weak region thereof. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a microwave plasma processing apparatus that generates plasma using microwaves and performs plasma processing on an object to be processed. In particular, the present invention relates to a surface shape of a dielectric plate that transmits microwaves in order to introduce microwaves into a processing container.

  A microwave plasma processing apparatus has been proposed as one of plasma processing apparatuses for performing a film forming process or an etching process on an object to be processed using plasma. Microwaves used in this apparatus are output from a microwave source, propagate through rectangular waveguides or coaxial waveguides, pass through a dielectric plate provided on the ceiling surface of the plasma processing apparatus, and enter the processing container. It is thrown. The electric field energy of the input microwave is consumed to excite the gas, thereby generating low temperature and high density plasma. If low-temperature and high-density plasma is used, fine processing can be performed on the object to be processed with high accuracy, and the process window can be widened.

  In recent developments of microwave plasma processing apparatuses, one of the major challenges is to cope with the increase in size of substrates. In other words, even if the microwave plasma processing apparatus is increased in size with an increase in the size of the substrate, plasma that can stably generate uniform plasma on the substrate and thereby perform high-quality plasma processing on the entire substrate. A processing unit is requested. However, when the area of the dielectric plate arranged on the ceiling surface of the device is increased with the increase in size of the device, it is difficult to uniformly generate a standing wave of the surface wave over the entire lower surface of the dielectric plate. The intensity of the electric field energy of the microwave on the lower surface is generated, and the density of the plasma generated in the portion where the energy is strong becomes higher than the density of the plasma generated in the portion where the energy is weak, making it difficult to generate a uniform plasma.

  On the other hand, instead of installing a single large-area dielectric on the ceiling surface of the processing vessel, each dielectric of multiple dielectric plates is partitioned by metal beams and installed on the ceiling surface at even intervals. A microwave plasma processing apparatus has been proposed (see, for example, Patent Document 1). According to this, the surface wave generated on the lower surface of the dielectric plate cannot propagate beyond the metal beam to the adjacent dielectric plate. In this way, by suppressing the generation of standing waves of surface waves propagating on the lower surface of the dielectric plate, the electric field energy of the microwaves supplied to the lower surface of each dielectric plate is made uniform, and a large area Uniform plasma can be stably generated over the entire upper portion of the substrate.

For example, in the microwave plasma processing apparatus, a plurality of recesses are formed on the lower surface of each dielectric plate 31 as shown in the upper portion of FIG. 4 with the lower surface (upper) and the cross section (lower) of the dielectric plate 31. . The intensity of the electric field energy of the microwave emitted from the lower surface of the dielectric plate into the processing container tends to increase depending on the distance from the feeding point and increases on the side surface of the recess. By taking these into consideration, the depth of each concave portion is made different, whereby the intensity of the electric field energy of the microwave emitted from the lower surface of the dielectric plate 31 can be made uniform. Thereby, it is possible to stably generate the plasma so that the uniform plasma spreads over the entire enlarged substrate.
JP 2007-103519 A

  However, the distribution of the electric field energy inside the dielectric plate 31 and the electric field energy of the microwaves emitted from the lower surface of the dielectric plate 31 change according to the state of the plasma, and the state of the plasma changes depending on the gas type. Therefore, the distribution of the electric field energy of the microwaves inside and under the dielectric plate 31 changes depending on the gas type. Therefore, if the shape of the unevenness formed on the lower surface of the dielectric plate 31 is not optimized depending on the gas type, the intensity of the electric field energy of the microwave is uniform in the inside and the lower surface of the dielectric plate with respect to the desired gas type. There is a case that cannot be made.

  For example, the standing wave ST inside the dielectric plate 31 shown in FIG. 4 shows the distribution of the electric field energy of the microwave inside the dielectric, and the state is the position of the feeding point P, the material of the dielectric plate 31 , Not only the size and dielectric constant, but also the incident wave μ of the microwave, the reflected wave rb from the beam 26 supporting the dielectric plate 31, and the reflected wave rp from the plasma.

  Of these factors, values other than the reflected wave from the plasma are determined at the design stage and do not change thereafter. On the other hand, the reflected wave rp from the plasma varies depending on the state of the plasma. Therefore, the state of the standing wave ST inside the dielectric plate 31 varies according to the reflected wave rp from the plasma.

As described above, the plasma state (plasma impedance) varies depending on the gas type, and can be expressed by the dielectric constant ε _r and the dielectric loss tangent T _{δ of the} plasma. From the above, it can be seen that the energy distribution inside the dielectric plate 31 varies depending on the gas type, and the difference in the energy distribution can be predicted by the dielectric constant ε _r and the dielectric loss tangent T _δ of the plasma.

  Therefore, in consideration of the fact that the energy distribution inside the dielectric plate 31 varies depending on the gas type, when the unevenness on the lower surface of the dielectric plate is optimized with respect to the reference gas, the lower surface of the dielectric plate is matched to the gas type. It is necessary to optimize the unevenness of the dielectric plate so that the inside of the dielectric plate 31 has a uniform energy distribution.

  In order to solve the above problems, the present invention provides a microwave plasma processing apparatus in which the surface shape of a dielectric plate on the object side is optimized according to the gas type.

  That is, in order to solve the above-described problems, according to an aspect of the present invention, a processing vessel in which plasma is excited inside, and a microwave that supplies microwaves necessary for exciting the plasma in the processing vessel. There is provided a microwave plasma processing apparatus including a wave source and a plurality of dielectric plates facing the inside of the processing container and propagating microwaves supplied from the microwave source into the processing container.

  Two or more recesses or protrusions are formed on the surface of each dielectric plate provided in the microwave plasma processing apparatus that faces the object to be processed. The unevenness is based on the distribution of electric field energy in each dielectric plate predicted according to the reflected wave from the plasma. It is formed so that energy is transmitted to the weak area.

As described above, the state of the standing wave inside the dielectric plate varies depending on the reflected wave from the plasma. The reflected wave from the plasma varies depending on the state of the plasma. The plasma state varies depending on the gas species, and can be expressed by the dielectric constant ε _r and the dielectric loss tangent T _{δ of the} plasma. That is, the standing wave inside the dielectric plate changes depending on the gas type, and the state can be predicted from the dielectric constant ε _r of the plasma generated when the desired gas is excited and the dielectric loss tangent T _{δ of the} plasma. it can.

  Therefore, in the dielectric plate according to the present invention, first, two or more concave portions or convex portions serving as a reference are formed corresponding to the reference gas, and the gas type used in the actual process is formed with respect to the reference unevenness. Processing (optimization, customization) according to

Specifically, the state of the standing wave inside the dielectric plate, that is, the distribution of the electric field energy inside the dielectric plate, is determined by the plasma dielectric constant ε _r and the dielectric loss tangent T _{δ that} are predetermined according to the gas type. And the reference unevenness on the surface of each dielectric plate is flattened so that the energy is transmitted from the strong region to the weak region on the lower surface of the dielectric plate based on the predicted electric field energy distribution.

  For example, when the electric field energy at the center portion inside the dielectric plate is stronger than the electric field energy at both end portions, as shown in the upper portion of FIG. 4, the convex portions F at both ends of the reference unevenness are shown in the lower portion of FIG. And flatten by scraping. As a result, the microwave surface wave SW propagates from the stronger electric field energy toward the weaker one in the recesses H12 and H67 which are flattened by shaving. Thereby, the electric field energy E is transmitted toward the outside of the lower dielectric. As a result, the electric field energy outside the dielectric increases also inside the dielectric, and the state of the standing wave ST inside the dielectric plate becomes uniform as shown in the lower part of FIG. 4 (that is, the dielectric plate The internal electric field energy becomes uniform), and a uniform plasma can be generated in a process using a desired gas species.

  As a method for flattening two or more irregularities formed on the surface of each dielectric plate facing the object to be processed, at least a concave portion or a convex portion formed in a region where the electric field energy changes from a strong region to a weak region is used. A part may be flattened.

  For example, as shown in FIG. 4, all of the convex portions F between the region where the electric field energy is strong and the region where the electric field energy is weak may be completely flattened, as shown in FIGS. 7 (a) and 7 (b). As shown, only the center part FC of the convex part or both end parts FE of the convex part may be made flat.

  When part of the convex part is flattened, the propagation efficiency of the surface wave SW is lower than when all the convex parts are flattened, so that the electric field energy E is appropriately transmitted from a strong field energy region to a weak region. Can do. However, since the electric field tends to concentrate near the side surface of the concave portion, the propagation efficiency increases when the both ends FE of the convex portion are flattened than when the central portion FC of the convex portion is flattened.

  Further, as shown in FIG. 7C, all the flattening of the convex portions and some flattening may be combined according to the electric field energy distribution inside the dielectric plate 31. This also allows the surface wave SW to propagate to a desired level on the lower surface of the dielectric plate.

  The microwave plasma processing apparatus propagates the microwave supplied from the microwave source to one or more waveguides, passes the plurality of slots adjacent to the waveguide, and is adjacent to the plurality of slots. The apparatus may be configured to be propagated to the plurality of dielectric plates and supplied into the processing container.

  The microwave plasma processing apparatus may cause the microwave supplied from the microwave source to propagate to one or more conductor rods and further propagate to the plurality of dielectric plates adjacent to or close to the conductor rods. The apparatus may be configured to supply into the processing container.

  As described above, according to the present invention, the shape of the dielectric plate provided facing the inside of the processing container of the microwave plasma processing apparatus is optimized by the gas type, so that the desired gas type can be obtained. Accordingly, plasma can be generated uniformly.

BEST MODE FOR CARRYING OUT THE INVENTION

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the following description and the accompanying drawings, the same reference numerals are given to the constituent elements having the same configuration and function, and redundant description is omitted.

(First embodiment)
First, the configuration of the microwave plasma processing apparatus according to the first embodiment of the present invention will be described with reference to FIGS. 1 and 2. FIG. 1 schematically shows a longitudinal sectional view of the apparatus cut in a direction perpendicular to the y-axis, and FIG. 2 shows a ceiling surface of the apparatus. In the following description, a process of forming an amorphous silicon film by a CVD (Chemical Vapor Deposition) process using the microwave plasma processing apparatus according to the present embodiment will be described as an example.

(Configuration of microwave plasma processing equipment)
The microwave plasma processing apparatus 100 includes a processing container 10 and a lid 20. The processing container 10 has a bottomed cubic shape whose upper part is opened. The processing container 10 and the lid 20 are sealed by an O-ring 32 disposed between the lower surface outer periphery of the lid 20 (lid body 21) and the upper surface outer periphery of the processing container 10, thereby A processing chamber U for performing plasma processing is formed. The processing container 10 and the lid 20 are made of a metal such as aluminum, for example, and are electrically grounded.

  The processing container 10 is provided with a susceptor 11 (mounting table) for mounting a glass substrate (hereinafter referred to as “substrate”) G therein. The susceptor 11 is made of, for example, aluminum nitride, and a power feeding unit 11a and a heater 11b are provided therein.

  A high frequency power source 12b is connected to the power supply unit 11a via a matching unit 12a (for example, a capacitor). In addition, a high-voltage DC power supply 13b is connected to the power supply unit 11a via a coil 13a. The matching unit 12a, the high-frequency power source 12b, the coil 13a, and the high-voltage DC power source 13b are provided outside the processing container 10. The high frequency power supply 12b and the high voltage DC power supply 13b are grounded.

  The power feeding unit 11a applies a predetermined bias voltage to the inside of the processing container 10 by the high frequency power output from the high frequency power source 12b. The power feeding unit 11a is configured to electrostatically attract the substrate G with a DC voltage output from the high-voltage DC power supply 13b.

  An AC power supply 14 provided outside the processing container 10 is connected to the heater 11b, and the substrate G is held at a predetermined temperature by an AC voltage output from the AC power supply 14.

  The bottom surface of the processing container 10 is opened in a cylindrical shape, and one end of a bellows 15 is attached to the periphery of the bottom surface. The other end of the bellows 15 is fixed to the elevating plate 16. In this way, the opening at the bottom of the processing container 10 is sealed by the bellows 15 and the lifting plate 16.

  The susceptor 11 is supported by a cylindrical body 17 disposed on the lifting plate 16 and moves up and down integrally with the lifting plate 16 and the cylindrical body 17. Thereby, the susceptor 11 is adjusted to a height corresponding to the processing process. A baffle plate 18 for controlling the gas flow in the processing chamber U to a preferable state is provided around the susceptor 11.

  A vacuum pump (not shown) provided outside the processing container 10 is provided at the bottom of the processing container 10. The vacuum pump is configured to depressurize the processing chamber U to a desired degree of vacuum by discharging gas from the processing container 10 through the gas discharge pipe 19.

The lid 20 is provided with a lid body 21, six waveguides 33, a slot antenna 30, and a plurality of dielectric plates 31. The six waveguides 33 have a rectangular cross-sectional shape and are provided in parallel inside the lid body 21. The inside is filled with a dielectric member 34 such as fluororesin (for example, Teflon (registered trademark)), alumina (Al ₂ O ₃ ), quartz or the like, and λg ₁ = λc / (ε ₁ ) by the dielectric member 34. ^The guide wavelength λg ₁ of each waveguide 33 is controlled according to the expression of ^1/2 . Here, λc is the wavelength of free space, and ε ₁ is the dielectric constant of the dielectric member 34.

  Each waveguide 33 is opened at the top, and a movable portion 35 is inserted into the opening so as to be movable up and down. The movable portion 35 is made of a conductive material that is a non-magnetic material such as aluminum.

  An elevating mechanism 36 is provided on the upper surface of each movable portion 35 outside the lid main body 21 so that the movable portion 35 is moved up and down. With this configuration, the height of the waveguide 33 can be arbitrarily changed by moving the movable portion 35 up and down with the upper surface of the dielectric member 34 as the limit.

The slot antenna 30 is formed integrally with the lid body 21 below the lid body 21. The slot antenna 30 is made of a metal that is a nonmagnetic material such as aluminum. In the slot antenna 30, the 13 slots 37 (openings) shown in FIG. 2 are arranged in series on the lower surface of each waveguide 33. Each slot 37 is filled with a dielectric member such as fluororesin, alumina (Al ₂ O ₃ ), quartz, and the like, and according to the equation: λg ₂ = λc / (ε ₂ ) ^1/2 The guide wavelength λg ₂ of each slot 37 is controlled. Here, λc is the wavelength of free space, and ε ₂ is the dielectric constant of the dielectric member inside the slot 37.

(Dielectric plate)
As shown in FIG. 2, 39 dielectric plates 31 are equally installed facing the inside of the processing container 10. Each dielectric plate 31 is formed in a tile shape, and 13 dielectric plates 31 are provided in three rows at the same pitch so as to straddle the two waveguides 33. The six waveguides 33 are connected to the three microwave sources 40 through the Y branch tube 41 in pairs. Each dielectric plate 31 is adjacent to two slots 37. As a result, a microwave propagation path composed of the six waveguides 33, the plurality of slots 37, and the plurality of dielectric plates 31 is constructed.

  With the above configuration, a total of 39 (= 13 × 3 rows) dielectric plates 31 are attached to the lower surface of the slot antenna 30. The number of slots 37 formed on the lower surface of each waveguide 33 is arbitrary. For example, twelve slots 37 are provided on the lower surface of each waveguide 33, and the lower surfaces of the slot antennas 30 are all provided. 36 (= 12 × 3 rows) dielectric plates 31 may be disposed.

  As shown in FIGS. 1 and 3, each dielectric plate 31 has irregularities formed on the surface facing the substrate G. The intensity of the electric field energy of the microwave emitted into the processing container depends on the position of the feeding point and becomes stronger on the side surface of the recess formed on the lower surface of the dielectric plate 31. For this reason, the depth of each recessed part is set to a different value in consideration of these. The optimization of the unevenness on the lower surface of the dielectric plate 31 will be described later.

  As shown in FIGS. 1 and 2, a beam 26 formed in a lattice shape is provided on the lower surface of the slot antenna 30 to support 39 dielectric plates 31. The beam 26 is formed of a nonmagnetic material such as aluminum.

  As shown in FIG. 3, the gas nozzles 27 and 28 are fixed to the beam 26 so as to hang down from the beam 26. The gas nozzle 27 is a mushroom screw and is made of metal. A hollow gas passage is provided inside the gas nozzle 27. Argon gas is blown sideways from the gas hole A of the gas nozzle 27 directly below the dielectric plate 31.

  The gas nozzle 28 is a rod-shaped (cylindrical) screw, and is made of metal. A hollow gas passage is provided inside the gas nozzle 28. Silane gas and hydrogen gas are blown downward downward from the position where the argon gas is blown from the gas hole B of the gas nozzle 28.

  Returning to FIG. 1 again, the description will be continued. The processing gas supply source 43 includes a plurality of valves (valves 43a1, 43a3, 43b1, 43b3, 43b5, 43b7), a plurality of mass flow controllers (mass flow controllers 43a2, 43b2, 43b6), an argon gas supply source 43a4, a silane gas supply source 43b4, and It is comprised from the hydrogen gas supply source 43b8.

  The processing gas supply source 43 supplies desired concentrations of argon gas, silane gas, and hydrogen gas into the processing container 10 by controlling the opening and closing of the valves and the opening of each mass flow controller, respectively.

  The gas passage 29 a penetrates the inside of the beam 26 and is connected to the gas passage of the gas nozzle 27. As a result, the argon gas supply source 43a4 communicates with the gas hole A through a single pipe. The gas passage 29 b also penetrates the inside of the beam 26 and is connected to the gas passage of the gas nozzle 28. As a result, the silane gas supply source 43b4 and the hydrogen gas supply source 43b8 communicate with the gas hole B through a single pipe.

  A cooling water supply source 45 disposed outside the microwave plasma processing apparatus 100 is connected to the cooling water pipe 44, and the cooling water supplied from the cooling water supply source 45 circulates in the cooling water pipe 44. By returning to the cooling water supply source 45, the lid body 21 is kept at a desired temperature.

  With the configuration described above, the argon gas blown immediately below the dielectric plate 31 is first excited by, for example, 2.45 GHz × 3 microwaves output from the three microwave sources 40 shown in FIG. Then, it is turned into plasma immediately below each dielectric plate 31.

After the argon gas is ignited by plasma, the silane gas and hydrogen gas blown down from the argon gas consume a certain amount of energy for the plasma conversion of the argon gas to form a high-quality film by the weakened electric field energy. The precursor (precursor) of SiH ₃ radical is dissociated, and the SiH ₂ radical is not dissociated. As a result, a high-quality amorphous silicon film can be formed by the action of the SiH ₃ radical.

(Optimization of the shape of the bottom surface of the dielectric plate)
Next, optimization of the unevenness provided on the lower surface of the dielectric plate 31 will be described in detail with reference to FIG.

  In the upper part of FIG. 4, argon gas is taken as a reference gas, and when generating plasma from the argon gas, the lower surface of the dielectric plate 31 so that the electric field energy intensity on the lower surface of the dielectric plate 31 is uniform. A lower surface (upper) and a cross-section (lower) of a dielectric plate 31 having an uneven shape are shown.

  When a gas other than argon gas is used depending on the process, it is necessary to optimize the reference unevenness according to the state of the standing wave ST inside the dielectric plate. Therefore, first, the standing wave ST inside the dielectric plate will be described.

  The state of the standing wave ST inside the dielectric plate indicates the distribution of the electric field energy of the microwave inside the dielectric plate, and not only the position of the feeding point P, the material, dimensions, and dielectric constant of the dielectric plate 31, but also the microwave source. , The reflected wave rb from the beam 26 supporting the dielectric plate 31, and the reflected wave rp from the plasma.

  Of these factors, values other than the reflected wave from the plasma are determined at the design stage and do not change thereafter. On the other hand, the reflected wave rp from the plasma varies depending on the state of the plasma. Therefore, it may be considered that the state of the standing wave ST inside the dielectric plate 31 changes according to the reflected wave rp (plasma impedance) from the plasma and hardly changes due to other factors.

Here, the reflected wave rp from the plasma varies depending on the gas type. Therefore, the standing wave ST inside the dielectric plate varies depending on the gas type, and it can be said that the state change can be predicted by the dielectric constant ε _r and the dielectric loss tangent T _δ of the plasma.

  The state change of the standing wave ST in the dielectric plate according to the change of the gas type is an index for optimizing (customizing) the unevenness of the lower surface of the dielectric plate 31 according to the gas type used in the actual process. Become.

  As shown in the upper part of FIG. 4, when the dielectric plate 31 with the unevenness optimized with respect to the reference gas (argon gas) is used in a process using a gas type other than the reference gas, the reference gas and the others For example, the electric field energy at both ends of the dielectric plate 31 is lower than the electric field energy at the center portion of the dielectric plate 31 due to the difference in the state of the standing wave ST inside the dielectric plate 31. In other words, there may be a non-uniform energy state. In this case, sufficient energy for plasma generation is not given to both ends of the dielectric plate 31. For this reason, the plasma density generated below both ends of the dielectric plate 31 is lower than the plasma density generated below the center of the dielectric plate 31.

Therefore, in the microwave plasma processing apparatus 100 according to the present embodiment, the state of the standing wave ST inside the dielectric plate 31 based on the plasma dielectric constant ε _r and the dielectric loss tangent T _δ determined in advance according to the gas type. Based on the predicted standing wave ST (that is, the distribution of the electric field energy inside the dielectric plate 31), the reference irregularities are processed so that the energy is transmitted from the strong region of the electric field energy to the weak region. (Flattened).

  Specifically, when the electric field energy at the central portion inside the dielectric plate is stronger than the electric field energy at both end portions, as shown in the upper part of FIG. As shown in Fig. 5, it is flattened by scraping. As a result, the microwave surface wave SW propagates from the stronger electric field energy toward the weaker one in the recesses H12 and H67 which are flattened by shaving. Thereby, the electric field energy E is transmitted toward the outside of the lower dielectric. As a result, the electric field energy outside the dielectric increases also inside the dielectric, and the state of the standing wave ST inside the dielectric plate becomes uniform as shown in the lower part of FIG. 4 (that is, the dielectric plate The internal electric field energy becomes uniform), and a uniform plasma can be generated in a process using a desired gas species.

In fact, the inventor confirmed by simulation how the plasma uniformity is obtained by optimizing the unevenness of the dielectric plate 31 according to the gas type. In the simulation, “hydrogen (H 2) gas, silane (SiH 4) gas” is assumed as a desired actual gas. The argon gas plasma has a dielectric constant ε _r of −200 and a dielectric loss tangent T _δ of −0.1. The dielectric constant ε _r of the actual gas plasma is −100 to −1 (optimum value −90), and the dielectric loss tangent T _δ is −0.3 to −0.05 (optimum value −0.05). .

  First, as shown in a perspective view, a cross-sectional view, and a bottom view in FIG. 5A, a simulation for generating plasma from real gas using the shape of the dielectric plate 31 optimized for argon gas is performed. went. The simulation result is shown in FIG.

  According to this, when the convex portions F are present at both ends of the lower surface of the dielectric plate 31, the dielectric plate 31 is optimized for argon gas. The amplitude of the standing wave ST became small at both ends of 31. That is, when plasma is generated from real gas using the dielectric plate 31 having an uneven shape optimized for argon gas, the electric field strength of the microwaves at both ends of the dielectric plate 31 is the microwave at the center of the dielectric plate 31. It was found to be lower than the electric field strength of. From this result, when the inventor uses the dielectric plate 31 optimized for argon gas for plasma conversion of the actual gas, the plasma in the vicinity of both ends of the dielectric plate 31 is larger than that in the central portion of the dielectric plate 31. It was found that the density was lowered and the plasma uniformity could not be maintained.

Therefore, the inventor decided to customize the reference dielectric plate 31 shown in FIG. The inventor has obtained a dielectric constant ε _r (for example, −90) and a dielectric loss tangent T _δ (for example, −0.05) of an actual gas plasma, and a dielectric constant ε _r −200 and a dielectric loss tangent T _{δ of} an argon gas plasma. From the difference from −0.1, it was calculated in advance which part of the concavo-convex shape of the lower surface of the dielectric plate 31 for argon gas should be flattened. Based on this content, the inventor customized the dielectric plate 31 for argon gas to the dielectric plate 31 for actual gas by scraping and flattening the convex portions F at both ends as shown in FIG. . And the inventor performed the simulation which produces | generates a plasma from real gas using the dielectric plate 31 for real gas. The simulation result is shown in FIG.

  According to this, since the dielectric plate 31 from which the convex portions F at both ends have been cut is optimized for real gas, it is most suitable for plasma conversion of real gas, and is fixed throughout the dielectric plate 31. The amplitude of the standing wave ST was constant. This is because there is no portion that is weak against electric field energy in the entire interior of the dielectric plate 31, and the energy is sufficiently distributed throughout the entire interior of the dielectric plate 31. The inventor considered this result as follows. That is, the surface wave of the microwave propagated from the stronger electric field energy toward the weaker one in the concave portion on the lower surface of the dielectric plate 31 flattened by removing the convex portions F at both ends. Thereby, the electric field energy E was transmitted toward the outside of the lower part of the dielectric. As a result, the electric field energy outside the dielectric also increases inside the dielectric, and the standing wave ST inside the dielectric plate 31 becomes uniform as shown in the lower part of FIG. 6 (that is, the dielectric In the process using the desired gas species, a uniform plasma could be generated.

In this way, the inventor has proved that the plasma uniformity can be improved by further optimizing the dielectric plate 31 having the irregular shape optimized for the argon gas for the actual gas. The inventor considered the reason as follows. When the gas species changes, the plasma permittivity ε _r and the dielectric loss tangent T _δ change. The dielectric constant ε _r of the plasma represents the state of polarization in the plasma, and the dielectric loss tangent T _δ of the plasma represents the state of charge loss due to resistance in the plasma generated by exciting the gas. That is, when the gas type changes, the plasma dielectric constant ε _r and the plasma dielectric loss tangent T _δ change, and when the gas type changes, the state of charge inside the plasma changes. Therefore, when the gas type changes, the magnitude of the reflected wave rp from the plasma changes accordingly. As a result, it was considered that the state of the standing wave inside the dielectric plate, that is, the state of electric field energy distribution inside the dielectric becomes non-uniform. From this consideration, it was concluded that optimization of the dielectric plate 31 is very useful for stably generating a uniform plasma for a desired gas species.

  As described above, according to the microwave plasma processing apparatus 100 according to the present embodiment, by mounting the dielectric plate 31 optimized for the gas type used in the process, the dielectric plate 31 The intensity of the electric field energy emitted from the lower surface can be made uniform, and as a result, uniform plasma can be generated.

(Modification)
In FIG. 4, all the convex portions F between adjacent concave portions are flattened. However, it is not always necessary to flatten all of the convex portions. For example, as shown in FIG. 7A or FIG. 7B, one of the convex portions such as the central portion FC or both end portions FE of the convex portion is formed. The part may be flattened. According to this, since the propagation efficiency of the surface wave SW is reduced as compared with the case where all of the convex portions are flattened, the electric field energy can be appropriately transmitted from the strong electric field energy region to the weak electric field energy region. However, since the electric field tends to concentrate near the side surface of the concave portion, the center portion FC of the convex portion in FIG. 7A is more flat when both ends FE of the convex portion in FIG. It can transmit higher electric field energy than flattening.

  Furthermore, as shown in FIG. 7C, all flattening of the convex portions and partial flattening may be combined depending on the strength of the electric field energy inside the dielectric. Also by this, the surface wave SW can be propagated to a desired degree, and plasma can be generated uniformly.

  As mentioned above, although preferred embodiment of this invention was described referring an accompanying drawing, it cannot be overemphasized that this invention is not limited to the example which concerns. It will be apparent to those skilled in the art that various changes and modifications can be made within the scope of the claims, and these are naturally within the technical scope of the present invention. Understood.

  For example, in the optimization of the dielectric plate according to the present invention, the convex portion is flattened by cutting, but the present invention is not limited to this, and the flattening may be performed by filling the concave portion.

  In addition, the microwave plasma processing apparatus according to the present invention can execute various processes such as CVD, etching, and ashing that finely process an object to be processed by plasma.

It is a longitudinal cross-sectional view of the microwave plasma processing apparatus concerning 1st Embodiment of this invention. It is the figure which showed the ceiling surface of the apparatus concerning the embodiment. It is the figure which expanded the dielectric plate vicinity of FIG. It is a figure for demonstrating optimization of the shape of a dielectric material board lower surface. It is the figure which showed the simulation model (FIG. 5 (a) is a reference | standard shape, FIG.5 (b) is the optimized shape). FIGS. 6A and 6B are diagrams showing simulation results (FIG. 6A shows a standard shape, and FIG. 6B shows an optimized shape). FIG. 7A to FIG. 7C are diagrams showing modified examples of the shape of the lower surface of the dielectric plate.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Processing container 11 Susceptor 20 Lid body 21 Lid body 26 Beam 27, 28 Gas nozzle 30 Slot antenna 31 Dielectric board 32 O-ring 33 Waveguide 37 Slot 40 Microwave source 43 Gas supply source 43a4 Argon gas supply source 43b4 Silane gas supply source 43b8 Hydrogen gas supply source 100 Microwave plasma processing equipment U Processing chamber G Substrate

Claims (9)

A processing vessel in which plasma is excited;
A microwave source for supplying microwaves necessary to excite plasma in the processing vessel;
A plurality of dielectric plates facing the inside of the processing vessel and propagating microwaves supplied from the microwave source into the processing vessel,
Each dielectric plate of the plurality of dielectric plates has two or more concave portions or convex portions formed on the surface of each dielectric plate facing the object to be processed.
Further, the surface of the surface of each dielectric plate facing the object to be processed is weakened from the region where the electric field energy is strong, based on the electric field energy distribution inside each dielectric plate predicted according to the reflected wave from the plasma. A microwave plasma processing apparatus for flattening at least a part of two or more concave portions or convex portions formed on a surface of each dielectric plate facing a target object so that energy is transmitted to the region.   The distribution of the electric field energy in each dielectric plate according to the reflected wave from the plasma is predicted from the dielectric constant of the plasma and the dielectric loss tangent of the plasma generated when a desired gas is excited. Microwave plasma processing equipment.   Of the two or more recesses or projections formed on the surface of each dielectric plate facing the object to be processed, at least the recesses or projections formed in the region where the electric field energy changes from the strong region to the weak region The microwave plasma processing apparatus according to claim 1, wherein a part of the plasma processing apparatus is planarized.   The microwave plasma processing apparatus according to claim 3, wherein all the concave portions or convex portions formed in a region where the electric field energy changes from a strong region to a weak region is flattened.   The microwave plasma processing apparatus according to claim 3, wherein a part of a concave portion or a convex portion formed in a region where the electric field energy changes from a strong region to a weak region is flattened.   The microwave plasma processing apparatus according to claim 5, wherein a central portion of a concave portion or a convex portion formed in a region where the electric field energy changes from a strong region to a weak region is flattened.   The microwave plasma processing apparatus according to claim 5, wherein both end portions of a concave portion or a convex portion formed in a region where the electric field energy changes from a strong region to a weak region are flattened.   In the microwave plasma processing apparatus, the microwave supplied from the microwave source is propagated to one or more waveguides, passed through a plurality of slots, and propagated to the plurality of dielectric plates. The microwave plasma processing apparatus according to any one of claims 1 to 7, which is supplied to the apparatus.   The microwave plasma processing apparatus causes the microwave supplied from the microwave source to propagate to one or more conductor rods and further propagates to the plurality of dielectric plates adjacent to or close to the conductor rods. The microwave plasma processing apparatus according to any one of claims 1 to 7, which is supplied into a container.